The present invention relates to a polishing slurry and a polishing method using the same. More specifically, the present invention provides a novel polishing slurry used for chemically and mechanically polishing a silicon dioxide film or metal film formed on a semiconductor substrate such as a silicon wafer, and a polishing method using the same.
As semiconductor devices are highly integrated, wiring techniques advance more and more toward fineness and multilayer. Advance toward fineness and multilayer in wiring increases a difference in a level between layers and steepens a gradient of wirings toward a substrate, so that a processing accuracy and a reliability of the wirings formed thereon tend to be lowered.
Chemical and mechanical polishing (hereinafter abbreviated as CMP) is paid attentions for solving the problems described above. A CMP method is a means for polishing an interlayer dielectric film such as a silicon dioxide film and a metal film of aluminum, tungsten or the like which forms a wiring layer to thereby planarize them in a production process of semiconductor devices. Less contamination of a material to be polished, smaller scratches, a higher polishing efficiency and a higher selectivity of polishing a silicon dioxide film are required to polishing slurrys used in CMP.
The preceding performances of the polishing slurrys depend largely on abrasive grain components such as silica and cerium oxide which are principal raw materials. For example, a polishing slurry using fumed silica for abrasive grains which has so far been often used has had the problem that while having an excellent purity, it produces a lot of scratches. It is known that when cerium oxide is used for abrasive grains, the polishing efficiency is high, but there has been the problem of the scratch and the purity.
For example, if scratches are produced in a CMP process, wirings of the device are broken or cause short circuit, and therefore it causes a sharp reduction in a yield of the device. When polishing slurrys having a poor purity are used, washing after polishing requires much time, and when washing is insufficient, it causes a reduction in a yield of the device.
Then, an object of the present invention is to provide a polishing slurry which produces less scratches and can prevent breaking and short circuit in wirings of the device and which can suitably be used for CMP.
Further, another object of the present invention is to provide a high purity polishing slurry which has a high polishing efficiency and less contaminates a material to be polished.
Still another object of the present invention is to provide a polishing slurry capable of being used at a neutral and acidic areas where polishing slurrys have not so far been able to be used.
The objects of the present invention described above can be achieved by a polishing slurry characterized by dispersing silica particles having an average primary particle size of 50 to 300 nm (nanometer) and a refractive index of 1.41 to 1.44 in water.